JPH0527291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a confidential message transmitting and receiving device for analog signals, and more particularly to a confidential message transmitting and receiving device that facilitates confidential message synchronization. Various confidential communication techniques have been developed to protect the confidentiality of communications. In particular, there are many types of secret techniques for concealing analog signals. In order to achieve the purpose of secret speech, it is sufficient to perform some kind of conversion on the transmitted signal, but in order to increase the strength of secret speech, the conversion operation must be changed over time. In order to obtain a transmitted signal by inversely converting the confidential message on the receiving side, the inverse confidential conversion must be performed in synchronization with the conversion operation that changed over time on the transmitting side. I need to take it.

In conventional analog secret communication technology, signals for synchronization were transmitted independently of analog signals. For example, there are separate random number generators on the transmitting and receiving sides, and we know how to synchronize by sending a synchronization signal before a conversation, and how to always send a synchronization signal together with the transmitted analog information. It is being Since the synchronization signal corresponds to the period of secret conversion, it is necessary to increase the period of secret conversion in order to increase the privacy strength. As a result, it takes a long time to establish synchronization, and at the same time, it requires a complicated synchronization circuit.

An object of the present invention is to provide a confidential message transmitting/receiving device that can synchronize between a transmitting device and a receiving device without transmitting synchronization information.

According to the present invention, means for generating a random number sequence, means for performing secret conversion into an analog signal to be transmitted in accordance with the discrete values generated by the random number sequence, and encrypting the random number sequence. a private message transmitting device comprising a self-synchronizing encoder; and means for transmitting a signal obtained by combining a discrete signal obtained from the encoder and an analog signal obtained from the means for performing private conversion; means for separating the analog signal and the discrete signal by performing a reverse operation of combining the analog signal and the discrete signal performed by the confidential transmission device; and a decoder for decoding the discrete signal. and a means for generating a discrete signal using the signal obtained from the decoder, and correspondingly performing an inverse operation of the encrypted speech conversion performed by the encrypted speech transmitting device, and a means for generating a signal obtained from the discrete signal. A confidential message receiving device characterized by receiving an analog signal; and a confidential message transmitting/receiving device are obtained.

Furthermore, according to the present invention, the discrete values generated for performing secret conversion by the means for performing secret conversion are generated by continuously inputting a random number sequence without dividing it into blocks. A secret message transmitting/receiving device having characteristics is obtained.

A detailed explanation will be given below using the drawings. FIG. 1 is a block diagram of an embodiment of a confidential message transmitting device according to the present invention, and FIG. 2 is a block diagram of an embodiment of a confidential message receiving device according to the present invention. An analog signal to be transmitted is inputted from an input terminal 1 and then inputted from a confidential conversion circuit 2, where conversion for confidential communication is performed. Specifically, the secret conversion may be any type of conversion; for example, a band division/exchange method may be used in which the input signal is divided into a plurality of bands and exchanged. At this time, many combinations can be considered for the replacement method. As a signal for selecting this combination, a discrete number generation circuit 4 is used which receives the output signal of the random number sequence generation circuit 3 as an input. This circuit can be realized, for example, as shown in FIG. The random number series is inputted from the input terminal 31 and is sequentially input to each stage 32, 33,
34. Now, if we consider a binary signal as a random number series, this circuit uses a three-stage shift register, so a total of eight combinations can be obtained. In the figure, the conversion circuit 35 generates a control signal for the secret conversion circuit at an output terminal 36 in accordance with the contents of the shift register, and uses this as a control signal input to the secret conversion circuit 2.

A part of the output signal of the random number sequence generation circuit 3 is input to the encryption circuit 5 and an encrypted output is obtained. A possible method for implementing the encryption circuit is, for example, a self-synchronized encryption method as shown in FIG. 4a. A random number sequence is inputted from an input terminal 41, and in the case of an N-value signal, an addition circuit 42 modulo N performs addition with an output signal of a function generation circuit 46, which will be explained separately, and a random number sequence is inputted from an output terminal 47. Output. At the same time, part of the output signal is transferred to shift registers 43 and 4.
4 and 45 are input sequentially. The function generating circuit 46 generates a signal uniquely determined by the contents of each shift register. The detailed operation is well known from cryptography and other fields, so it will not be explained here. Here, the operation of the encryption/decryption circuit 25 (FIG. 2) of the confidential message receiving apparatus will be explained using FIG. 4b. As will be explained later, the output sequence of the encryption circuit is received at the input terminal 48 of the encryption and decryption circuit on the receiving side. Part of the received signal sequence is sequentially input to shift registers 43, 44, and 45, and is also input to the function generation circuit 46 described earlier.
is added to the output by the adder circuit 42, and the same signal sequence as input to the encryption circuit 5 is obtained. This operation is easy to understand when considering a binary (0, 1) signal sequence, which is the easiest to implement in a circuit.
Now, if we ignore the signal delay, the shift registers 43 and 4 of the encryption circuit 5 and the encryption/decryption circuit 25
The same value is stored in 4 and 45, respectively.
Therefore, the outputs of each function generating circuit 46 will also generate the same value. 0 or 1 for the signal input to the input terminal 41 of the encryption circuit.
The value of will be added twice in a row. As is well known in addition modulo 2,
Even if you add 0 twice to the input signal, or add 1 twice
Even if you add degrees, the value does not change. Therefore, the same sequence as the input signal of the encryption circuit is obtained at the output terminal 49 of the decryption circuit. Even if someone attempting to eavesdrop can learn the output signal of the encryption circuit during communication, if they do not know the operation of the encryption/decryption circuit, especially the operation of the function generation circuit 46, they will not be able to know the original signal. It is not possible. The operations of the encryption circuit and decryption circuit described above are no different from conventional encryption and decryption techniques, and the conventional techniques can be used as is.

Return to Figure 1 again. The secret message signal output from the secret message conversion circuit 2, together with the output signal from the encryption circuit 5,
After being synthesized by the synthesis circuit 6, the output terminal 7
Sent from. Here, it is conceivable that the synthesis circuit 6 separates and synthesizes on the frequency axis, as shown in FIG. 5, for example. Figure a shows the power spectrum of the confidential analog signal, and Figure b shows the spectrum of the signal modulated with the encrypted discrete signal. Here, modulation is performed to separate frequency bands, and is not necessarily necessary, and may be simple frequency conversion. Other methods of combining may be considered, such as separation on the time axis; in any case, any method may be used as long as the two signals can be separated again on the receiving side.

As mentioned above, FIG. 2 is a block diagram showing an embodiment of the confidential message receiving apparatus according to the present invention. The signal received at the input terminal 21 is processed by the signal separation circuit 26 into a confidential analog signal combined on the transmitting side and an encrypted discrete signal. Specifically, for example, when the signals are separated and combined on the frequency axis as shown in FIG. 5, they can be separated using a low-pass filter and a high-pass filter. If modulation is performed using a discrete signal, demodulation shall also be performed.

The encrypted discrete signal is sent to the encryption/decryption circuit 25.
The transmitted random number sequence is obtained. This random number sequence is applied to the discrete number generation circuit 24, and its output becomes the control input of the confidential speech inverse conversion circuit 22. Here, the discrete numerical value generation circuit operates in the same manner as shown in FIG. It is. Therefore, for the same register contents, the contents of the discrete numerical value generation circuits on the transmitting side and the receiving side may be determined to be such numerical values that the secret conversion returns to the original value by inverse conversion. The transmitted analog signal is obtained at the output terminal 27 as the output of the private speech inverse conversion circuit 22.

As described above, in the present invention, the discrete information upon performing secret conversion is encrypted and transmitted.
On the receiving side, secret speech inverse conversion is performed using the information obtained by decoding the code. Therefore, there is no need to transmit any synchronization information. Therefore, there is an effect that the time required to establish synchronization or the synchronization circuit as in the prior art is not required. Furthermore, since there is no need for synchronization, there is no limit to the random number sequences that can be used; for example, random number sequences generated from physical noise can be used, which has the effect of making it possible to obtain an almost infinite number of private keys.

The random number sequence generation circuit used in the present invention does not need to be limited in any way, and may use, for example, a data signal to be transmitted or a signal obtained by encrypting the data signal. At this time, since the transmitted data signal is obtained as the output of the decryptor on the receiving side, there is also the effect that data transmission can be performed while having a conversation. In the conventional confidential communication system, for example, a synchronization signal is sent to the part (b) in Figure 5, so the band in this part is wasted, but in this case,
This band is also effectively used for data transmission.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a confidential message transmitting device constituting a confidential message transmitting/receiving device of the present invention, and FIG. 2 is a block diagram showing an embodiment of a confidential message receiving device constituting a confidential message transmitting/receiving device of the present invention. FIG. 3 is a block diagram showing an embodiment of a discrete numerical value generating circuit used in the present invention, FIG. 4a is an encryption circuit used in a confidential message transmitting device, and FIG. FIG. 5 is a spectral diagram showing the operation of an example of the signal combining circuit used in the present invention. In these figures, 1, 31, 41 are signal input terminals, 7, 27, 36, 47, 49 are signal output terminals, 2 is a secret conversion circuit, 3 is a random number generation circuit,
4 and 24 are discrete numerical value generation circuits, 5 is an encryption circuit, 6 is a synthesis circuit, 26 is a separation circuit, 25 is an encryption/decryption circuit, 22 is a private message inverse conversion circuit, 32, 3
3, 34, 43, 44, and 45 are registers, 35 is a conversion circuit, 42 is an addition circuit, and 46 is a function generation circuit.

Claims (1)

[Claims] 1. Means for generating a random number sequence, means for performing secret conversion into an analog signal to be transmitted in correspondence with discrete values generated by the random number sequence, and encrypting the random number sequence. a self-synchronized encryptor, and means for transmitting a signal obtained by combining a discrete signal obtained from the encryptor and an analog signal obtained from the means for performing the encrypting conversion; means for separating the analog signal and the discrete signal by performing a reverse operation of the synthesis of the analog signal and the discrete signal performed by the confidential transmission device; and a decoder for decoding the discrete signal. and a means for generating a discrete signal using the signal obtained from the decoder, and correspondingly performing an inverse operation of the encrypted speech conversion performed by the encrypted speech transmitter, and a signal obtained from the discrete signal. A secret message transmitting/receiving device comprising: a confidential message receiving device characterized in that the received analog signal is a confidential message receiving device; and a confidential message transmitting and receiving device. 2. The discrete values generated for exchanging secret information by the means for exchanging secret information are generated by continuously inputting a random number sequence without dividing it into blocks. Confidential transmission/reception device.